CIC voltage-gated anion channels function in organisms ranging from bacteria to animals. CLH-3b is a C. elegans CIC-type channel expressed in the worm oocyte. The biophysical properties of CLH-3b resemble those of mammalian CIC-2. CLH-3b is activated by serine/threonine dephosphorylation during oocyte meiotic maturation and in response to cell swelling. The type 1 phosphatases CeGLC-7alpha/beta and a newly identified Ste20 kinase, GCK-3, regulate CLH-3b. GCK-3 is a homolog of mammalian PASK, which regulates K-CI and Na-K-2CI cotransporters that are involved in epithelial fluid and electrolyte transport, cell volume control and intracellular Cl- homeostasis. gck-3 and clh-3 are co-expressed in the worm oocyte and fluid secreting excretory cell or "kidney". Knockout of GCK-3 constitutively activates CLH-3b in non-maturing oocytes and causes fertility defects and profound disruption of whole animal fluid balance. My long-term goal is to define the signaling cascades in which GCK-3 functions to regulate CLH-3b and associated salt and water transport processes. Defining these pathways will provide significant and novel insights into CIC regulation and fundamental physiological processes including epithelial Cl- and fluid transport. I will use a combination of molecular biology, forward and reverse genetic analyses, and patch clamp electrophysiology to identify GCK-3 signaling components.